An Overview Of Algae Biofuel Production And Potential Environmental Impact

An Overview of Algae Biofuel Production and Potential
Environmental Impact
Marc Y. Menetrez*
Office of Research and Development, National Risk Management Research Laboratory, Air Pollution Prevention and Control
Division, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, United States
ABSTRACT: Algae are among the most potentially significant sources of
sustainable biofuels in the future of renewable energy. A feedstock with
virtually unlimited applicability, algae can metabolize various waste streams
(e.g., municipal wastewater, carbon dioxide from industrial flue gas) and
produce products with a wide variety of compositions and uses. These products
include lipids, which can be processed into biodiesel; carbohydrates, which can
be processed into ethanol; and proteins, which can be used for human and
animal consumption. Algae are commonly genetically engineered to allow for
advantageous process modification or optimization. However, issues remain
regarding human exposure to algae-derived toxins, allergens, and carcinogens
from both existing and genetically modified organisms (GMOs), as well as the
overall environmental impact of GMOs. A literature review was performed to
highlight issues related to the growth and use of algal products for generating
biofuels. Human exposure and environmental impact issues are identified and discussed, as well as current research and
development activities of academic, commercial, and governmental groups. It is hoped that the ideas contained in this paper will
increase environmental awareness of issues surrounding the production of algae and will help the algae industry develop to its full
potential.
I. BACKGROUND
Algae belong to a large, diverse group of organisms ranging
from unicellular to multicellular that produce complex organic
compounds from basic inorganic molecules using energy from
photosynthesis, inorganic chemical reactions, and heterotrophic
fermentation.1−3
The algae fossil record dates back approx-
imately three billion years, well into the Precambrian period.
Algae are ubiquitous within the biosphere and have generated a
large fraction of the oxygen present in the earth’s atmosphere
and a large quantity of organic carbon in the form of coal and
petroleum.2
Algae’s role in the development of the earth’s
biosphere was of unique importance.
The importance of algae has increased with the search for
renewable energy sources. Even under highly unfavorable
growth conditions, algae can thrive and produce valuable
byproducts such as lipids (oils), carbohydrates, proteins, and
various feedstocks that can be converted into biofuels and other
useful materials.4−6
Hu et al. (2008) projected a possible yield
of 200 barrels of oil per hectare (2.47 acres) of land used for
growing photosynthetic algae.5
This theoretical maximum algae
yield is 100 times greater than that for soybeans, a commonly
used feedstock for biodiesel, and is greater than any
demonstrated yield (by a factor of 10−20), but should be a
goal for the rapidly developing algae industry.5
Algae-based biofuel production has a number of potential
advantages:
• Biofuels and byproducts can be synthesized from a large
variety of algae.
• Algae have a rapid growth rate.
• Algae can be cultivated in brackish coastal water and
seawater.
• Some land areas that are unsuitable for agricultural can
be used to cultivate algae.
• Algae nutrient uptake uses high nitrogen, silicon,
phosphate, and sulfate nutrients from human or animal
waste.
• Algae can sequester carbon dioxide (CO2) from
industrial sources.
Developing this technology into a commercial success,
however, will be a challenge. Many issues must be addressed
for the algae industry to advance from its current state to
commercial success. Of these issues, environmental impact is
paramount. Algae production has demonstrated many positive
environmental effects as well as the potential for negative effects
on human health and the environment.
Numerous benchtop experiments and pilot projects have
been conducted and small-scale production facilities and
theoretical process models and projections have been
established.5,7−10
However, little extensive information has
been published detailing algae production processes or algae-
derived biofuel research and development that has been put
Received: March 20, 2012
Revised: June 5, 2012
Accepted: June 8, 2012
Published: June 8, 2012
Critical Review
pubs.acs.org/est
This article not subject to U.S. Copyright.
Published 2012 by the American Chemical
Society
7073 dx.doi.org/10.1021/es300917r | Environ. Sci. Technol. 2012, 46, 7073−7085

into practice. Often, the existing literature either is specific to a
unique example or is broader in scope. Additionally, what little
published information there is often fails to describe the
importance of algae production, how that information fits into
the present state of knowledge, or what environmental impacts
might result from expansion of the algae industry.
This paper provides a review of algae generation, the
products derived from algae, and the environmental and human
health issues surrounding the production process. This review
summarizes information related to the status of algae-based
biofuel research and development efforts, including the efforts
of a number of commercial biofuel companies that are using
genetic advancements to move in new directions. These unique
genetic advancements are fueling algae biofuel research and
making it an ever-changing area of activity with enormous
potential environmental consequences. In addition, the risk of
exposure to humans and the environment posed by algae
biofuel production is summarized and a number of prominent
forms of algae production are addressed and compared.
1. Nature of Algae. Algae lack the many distinct organs
and structures that characterize land plants, such as leaves,
roots, a waxy cuticle, and other organs.1,2
All algae contain
green chlorophyll; however, they are masked by photosynthetic
pigments that give them a distinguishing color that is used to
identify key divisions.1,2
These photosynthetic pigments are
made of four different kinds of chlorophyll: blue, red, brown,
and gold.1,2
Some algae are microscopic and are able to float in
surface waters (phytoplankton) due to their lipid content, while
others are macroscopic and attach to rocks or other structures
(seaweeds).2
Algae range in size from less than the size of
bacteria (0.5 μm) to over 50 m long.2
Algae are cultivated in a variety of aqueous systems, from
open air ponds to closed photobioreactors with closely
controlled environments.2,11,12
The temperature range needed
to support algal growth is specific to the species and strain
cultured. The optimal temperature for phytoplankton is within
the range of 20−30 °C. Temperatures lower than 16 °C will
slow growth, and temperatures higher than 35 °C are normally
lethal for a number of species.2,13,14
2. Constituents and Byproducts. The algal growth cycle
has demonstrated considerable flexibility in the biochemical
ability of algal cells to manufacture various useful compounds.
Depending on the species and growing conditions, algae can
yield a wide array of byproducts such as lipids, carbohydrates,
and proteins.15
Lipids are long carbon chain molecules that
serve as a structural component of the algal cell membrane. The
increased lipid content decreases the specific gravity, making
the algal cell buoyant. The buoyant algal cell then moves up in
the water column toward the solar energy source. Algal species
vary in lipid production from 20 to 80% (dry weight (DW)).
Adjusting the specific species growth requirements can affect
the algal biomass lipid, protein, and carbohydrate content.12
These adjustments include environmental culture conditions
such as process velocity, length of the growth period, and
nutrient supply.15−17
Becker listed the constituents of 17 common algal species.16
The constituents of lipids, starches, and proteins are listed in
Table 1. As the table shows, these constituents vary
substantially depending on the substrate and environmental
conditions of the algal biomass composition.16
Lipids extracted from microalgae can be used to produce
biodiesel.12
Once the lipids have been extracted, the leftover
solids are composed of mostly carbohydrates and proteins.
Carbohydrates such as starches and sugars can be fermented to
produce ethanol.18
If algal oil is extracted for production of
biodiesel fuel, producing ethanol can facilitate this process by
becoming a key component of the transesterification process.
Transesterification of algal oil can be accomplished with
ethanol and sodium ethanolate, which serves as a catalyst.
The sodium ethanolate can be produced by reacting ethanol
with sodium. The catalyst sodium ethanolate and ethanol react
with the algal oil to produce biodiesel and glycerol.18
Microalgae belonging to several different families possess the
ability to produce and accumulate a large fraction of their dry
mass as lipids, as listed in Table 2.7,17,19
In microalgae, high
cellular lipid content is often achieved under environmental
stress, which can be caused by limitations of nitrogen,
phosphorus, silicon, salinity, and iron.20−24
Lipid accumulation
in the cells also depends on the growth phase of cells.25−28
Proteins are biochemical compounds made of one or more
peptides (a single linear polymer chain of amino acids) folded
into a solid or fibrous form. Studies have shown that algal
proteins are of high nutritional quality and are comparable to
the protein found in conventional vegetables. Forms of
macroalgae are commonly used for human consumption,
Table 1. Constituents of Algae (% of Dry Matter)16
algae lipids protein carbohydrate
Anabaena cylindrica 4−7 43−56 25−30
Aphanizomenon flos-aquae 3 62 23
Arthrospira maxima 6−7 60−71 13−16
Botryococcus braunii 86 4 20
Chlamydomonas rheinhardii 21 48 17
Chlorella ellipsoidea 84 5 16
Chlorella pyrenoidosa 2 57 26
Chlorella vulgaris 14−22 51−58 12−17
Dunaliella salina 6 57 32
Euglena gracilis 14−20 39−61 14−18
Prymnesium parvum 22−38 30−45 25−33
Porphyridium cruentum 9−14 28−39 40−57
Scenedesmus obliquus 12−14 50−56 10−17
Spirulina maxima 6−7 60−71 13−16
Spirogyra sp. 11−21 6−20 33−64
Spirulina platensis 4−9 46−63 8−14
Synechococcus sp. 11 63 15
Table 2. Oil Content of Microalgae7,19
microalgae oil content (% dry weight)
Botryococcus braunii 25−75
Chlorella sp. 28−32
Crypthecodinium cohnii 20
Cylindrotheca sp. 16−37
Dunaliella primolecta 23
Isochrysis sp. 25−33
Monallanthus salina >20
Nannochloris sp. 20−35
Nannochloropsis sp. 31−68
Neochloris oleoabundans 35−54
Nitzschia sp. 45−47
Phaeodactylum tricornutum 20−30
Schizochytrium sp. 50−77
Tetraselmis sueica 15−23
Environmental Science & Technology Critical Review
dx.doi.org/10.1021/es300917r | Environ. Sci. Technol. 2012, 46, 7073−7085
7074

while microalgal preparations are marketed as health food,
cosmetics, and animal feed.15,16,29
Algae production can also yield additional secondary benefits
such as the generation of hydrogen or methane, which can be
used for transportation fuels. Other benefits of algae production
can be gained from the removal of nitrogen and phosphorus
from the treatment of municipal, agricultural, and industrial
wastewater; the absorption of carbon dioxide from industrial
flue gas; the production of protein for human or animal
consumption; and the production of compounds for
pharmaceuticals, cosmetics, and aquaculture purposes.1,2,30−34
3. Environmental Conditions of Cultivation. Algae can
be cultivated in either open ponds or photobioreactors (PBRs).
Open pond systems are used for the majority of algae
cultivation, especially those strains with high oil content.25,35−37
PBRs are closed, controlled systems with equipment that
provides an ideal environment for high algae cultivation
productivity.25,35−37
Open ponds are generally categorized as either natural
waters, such as lakes, lagoons, and ponds, or artificial ponds or
containers. These include shallow ponds and tanks that are
circular or parallel raceway ponds (PRPs).25,35−38
Major
advantages of open ponds are that they are easy to construct
and operate and their costs are minimal. However, major
limitations of open ponds stem from the lack of control, which
can result in poor light utilization by microalgal cells (low
surface to volume ratio), evaporative losses, and poor diffusion
of CO2 to the atmosphere. These systems also require use of
large land areas, and they are highly susceptible to environ-
mental fluctuations such as swings in temperature and pH.
Microorganism contamination, such as the invasion of fast-
growing heterotrophic algae and bacteria, poses a significant
problem in open pond systems and has restricted their
successful use for commercial production of algae.25,35−38
The nature of open ponds and their susceptibility to
contamination have limited this application to mainly three
taxa: Spirulina, Dunaliella, and Chlorella.39
Research efforts to
deal with the problem of contamination involve the genetic
modification of microalgae.7,40−42
Processes using genetically
modified microalgae are currently being developed by many
biofuel industry participants.
Many scientific and commercial algae production efforts use
PBRs, which facilitate better control of the pure culture
environment by providing optimal growth requirements such as
amounts of carbon dioxide and water, temperature, exposure to
light, mixing, culture density, pH levels, and gas supply and
exchange rate.43,44
As these systems are closed, all of the
specific growth requirements are internally maintained.
PBRs pump the cultured organism and nutrient-laden water
through plastic or glass tubes that are exposed to sunlight. The
full spectrum of sunlight is generally not available to aquatic
algae, especially in high-density cultures and algae contained
within bioreactors.43,44
Light penetrates only the exposed 7.6−
10 cm due to turbidity caused by algae growth and media.43−46
A number of enclosed configurations, such as a helical-
tubular photobioreactor designed by Briassoulis et al.,47
are
being used to optimize the limiting growth conditions for
continuous production.32−34,47−52
The following conditions are
optimized in a PBR design:
• Volume size to surface area ratio (maximized for light
penetration).
• Containment to control temperature and pure culture
contaminants.
• Spatial distribution of fresh air and CO2.
• CO2 transfer rates (improved through extensive interface
surface between air and culture in liquid medium).
• Novel automated flow-through sensors (used to provide
continuous cell concentration monitoring).
PRP systems generally are perceived to be less expensive
than PBRs due to their lower construction and operation costs.
While these systems have been shown to be cost-effective for
limited applications such as producing protein, their low cost is
offset by their low biomass productivity and high vulnerability
due to technical constraints in pond design, separation, and
culture stability compared with PBRs.5,7,8
PBR systems have
higher construction and operational costs associated with the
culture process, but their algal cultures are capable of producing
a high lipid content biomass (40−55%).5,7,8
Given the
advantages and disadvantages of both systems, hybrid culture
systems are sometimes used to integrate the best aspects of
both systems.5,7,8,53−55
4. Genetically Modified and Enhanced Organisms.
The need to enhance or optimize production of target products
has led to the development of new forms of microalgae.
Consequently, as new forms of microorganisms increase, the
conversion steps necessary for biofuel production increase. In
the last two decades, molecular methods have been developed
to synthesize and clone genes and then transform or transfer
them into living organisms.56−59
All forms of microorganisms,
including microalgae, have undergone experimental modifica-
tions resulting in what are called genetically modified organisms
(GMOs), or genetically enhanced organisms (GEOs). These
techniques are generally known as recombinant DNA
technology, which creates new organisms with modified or
novel traits.56−62
Biotechnology research is developing GMOs to generate
biofuels directly or to produce intermediate organics that can
be converted into a biofuel. Examples of the former include
organics such as petroleum, ethanol, and hydrogen, while
intermediate organics include bot lipids (for processing into
biodiesel) and carbohydrates (for conversion into ethanol).
GMOs have also been developed to promote the breakdown of
plant fiber.61
New varieties of GMOs are being developed to
improve process speed, efficiency, and stability and simplify the
process; to enhance enzyme production; and, in the field, to
optimize plant feedstock production for use as energy crops.61
5. Growth Optimization. Research has also examined the
environmental conditions affecting microalgae growth.63,64
Many factors influence microalgae growth including irradiance,
culture temperature, algal biomass density, uniformity of
mixing, nutrient concentration, and culture age. Nutrients, for
example, specifically nitrogen, phosphorus, and sulfur, are
necessary for algae growth. Silica and iron, as well as several
trace elements, are also considered important marine nutrients
for growth. Unlike the growth of heterotrophic algae, which
remains constant, the productive growth of autotrophic
microalgae increases by daylight and decreases at night. The
losses are caused by respiration of carbohydrates (starch) and
glycogen, whereas the autotrophic input of metabolites is shut-
down. Additionally, the rates of growth of all forms of
microalgae are highly temperature dependent.38
Decreased irradiance and light penetration, which reduce
algae growth within PBRs can be caused by turbulent
7075

streaming, transverse mixing of the suspension layer on the
culture surface of thin-layer PBRs, increased viscosity of cell
suspension, sedimentation buildup, or the sticking of cells on
the surface of PBRs.63
For autotrophic cultivation in Trebon,
Czech Republic, with the maximum daily solar photosynthetic
active radiation (PAR), Doucha and Livansky63
obtained a near
linear rate of growth as a function of time, as shown in Figure 1.
As an example of the relationship between algae growth and
irradiance, Cyanobacterium anabaena (green-blue algae) was
studied by Gao et al.64
for growth responses under three
different solar radiation exposure treatments: (1) constant low
PAR (400−700 nm), (2) natural levels of solar radiation, and
(3) natural levels of solar radiation but without UV radiation
(290−400 nm). Although exposure to natural levels of PAR
exhibited increased growth, solar UV inhibited the growth up to
40%.64
This finding could lead to improved PBR design that
filters or excludes UV penetration.
The internal cellular storage of energy as oil rather than as
carbohydrates slows the reproduction rate of any algae. The
higher oil strains of algae grow slower than low oil strains. The
longer growth period makes the PRP culture process more
susceptible to contamination, but favors the PBR process.65
As
previously stated, in trying to maximize oil production with
algae, higher oil concentrations require longer growth periods
followed by a period of stress requiring nutrient restrictions.
However, the nutrient restrictions limit growth and the net
photosynthetic efficiency. To balance the growth and high oil
production, Huntley and Redalje39
used a combination of PBR
(for growth) and PRP (for nutrient stressing) using
Haematococcus pluvialis. The average biomass energy produc-
tion reported was 4542.5 L (1,200 gal) of biodiesel per acre-
year, which is greater than conventional oil-bearing crops such
as soybeans, which yield an average of 227 L (60 gal) of oil (or
approximately 151 L (40 gal) of biodiesel) per acre-year.39,65,66
An example methodology is illustrated with Neochloris
oleabundans, a freshwater microalga, which was grown in
continuously stirred PBRs at 30 °C, with CO2 supplementation
and illuminated by six fluorescent lamps (Philips TL-DM36W/
54-765).17
The lipid biomass concentration reached 56% (DW)
after 5 days of nitrogen starvation. An average lipid production
of 37.7 mg L−1
day−1
was obtained in a highly controlled
laboratory-scale setting.17
6. Extraction. After the growth of algae to their harvest
concentration, separation and extraction of the microalgal
biomass from the culture broth is required to use the oil,
alcohol, or target product. Biomass can be separated from the
broth by filtration, centrifugation, flocculation (colloidal
separation), and other means.55
In general, the cost of biomass
recovery can be considerable.7
A significant task involved with
the cultivation of microalgae is the difficulty in economically
harvesting and extracting the target product (such as oil) from a
dilute suspension.67
Depending on the specific algal organism
and the process employed, a substantial percentage of the
biomass generated can be in lipid oil.
The next step in the process involves the separation of lipid
oil from the rest of the algae biomass.55,68
One separation
technique is by crushing with an oil press. Commercial
manufacturers often use a combination of mechanical pressing
and chemical solvents to extract algae oil. Two other methods,
osmotic shock and ultrasonic extraction, cause the cell walls of
cells in a solution to rupture and release the lipid contents into
a solvent.53−55
Cyanobacteria (blue-green algae) are autotrophic microalgae
that require sunlight, CO2, and nutrients for energy and carbon.
GMO versions of these organisms have been given the ability to
transport primary metabolites such as ethanol or lipids across
membranes and the cell wall. The unique ability of the GMO
cyanobacteria cell to produce and secrete the target biofuel is
an example of an induced separation technique. It also presents
an overall strategy for making use of the organism over its
entire lifespan.69
Once the product is separated from the
organism, it is then further separated from the culture mix by
other techniques such as distillation for ethanol or oil−water
separation.66,68
7. Heterotrophic Algae Respiration and Fermenta-
tion. As many as 121 strains of algae (e.g., Chlamydomonas)
were studied by Gladue and Maxey29
for their ability to ferment
carbohydrates such as starches and sugars and produce lipids
while growing in the dark. These algae are called true
heterotrophs, because they use organic compounds as their
energy source as opposed to light-dependent autotrophs.
Solazyme, Inc., employs this heterotrophic algal culture to
manufacture oil, which is then processed into either algal oil to
yield biodiesel, HRF-76 jet fuel, or HRF-76 marine fuel.
Solazyme has already produced thousands of gallons of algal oil
and has refined algal oil into fuels that comply with applicable
ASTM D-975 specifications.70
Heterotrophic growth of microalgae requires carbohydrates
and oxygen (aerobic) and is typically one-third slower than
autotrophic growth. However, unlike the spatial limitations
found with PBRs regarding the transfer of light, heterotrophic
cultures can be grown in large-volume, dark, continuously
stirred tank reactors (CSTRs). Although heterotrophic CSTRs
are often referred to as fermentors, the growth production
process is a function of respiration and growth, not
fermentation (such as the production of ethanol from the
fermentation of sugars using yeast).71,72
In a bench-scale optimization study, Gao et al.73
were able to
generate a high lipid yield for biodiesel production using
glucose as the carbon source and heterotrophic growth of the
microalga Chlorella protothecoides. Using sorghum juice as the
glucose source yielded a lipid content of 5.1 g L−1
DW and
52.5%.73
These findings indicate that sweet sorghum juice is an
effective substrate for algal lipid and biodiesel production.
Sterility is a limiting factor in fermentor size and efficient
production technique. The volumes of fermentors commonly
used for industrial heterotrophic microalgal cultivation range
Figure 1. Algal mean cell concentration (DW) over time in a PBR.63
.
7076

from 80 to 200 m3
. These stirred-tank fermentors control
temperature, pH, and oxygen while using the desired algae
culture and carbohydrate. Sterility is first established by steam
sterilization (at 121 °C for 20 min) of the fermentor vessel, as
well as batch sterilization of all nutrient solutions, and use of a
pure microalgae starter culture.71,72
Batch and continuous cultivation techniques have been
demonstrated. The highest reported biomass culture densities
in heterotrophic productions are approximately 120 g L−1
(DW) for a three-day process or 40 g L−1
day−1
(DW), with
the average production being 70−100 g L−1
(DW) for a three-
day process or 23−33 g L−1
day−1
(DW). Additional varieties of
heterotrophic productivity are found in Chlorella sorokiniana
(green alga) at 24 g L−1
day−1
(DW) and Nitzschia alba
(diatom) at 19.2 L−1
day−1
(DW). Process productivity is not
easily compared due to differences in substrates, end points,
and product separation efficiencies.71,72
8. Biofuel Production. The potential for microalgae to
generate biofuel is augmented by their fast growth, reaching
maturity in as little as three days while producing in excess of
half their weight in oil.25,74
The production yield can vary
greatly depending on the algal culture, method (such as open
pond or PBR), reactor (batch, fed-batch, or continuous
operation), and culture technique (autotrophic or hetero-
trophic).
Algae have been cultivated to produce feedstocks needed for
the production of biofuels such as biodiesel, ethanol, and
petroleum.7
In fact, algae productivity is higher than that of
many energy crops (6−12 times greater than the energy
production for corn or switchgrass).75
The advantage of high
productivity is that the cultivation of algae requires a smaller
land area.7,76,77
High productivity and high lipid content make
algae a potentially important future source of biofuel.75
9. Biodiesel. Biodiesel is an alternative fuel that can be
produced from a variety of renewable sources. These sources
include canola oil, soybean oil, sunflower oil, cottonseed oil,
animal fats, and lipids produced by algae. Biodiesel is defined as
a monoalkyl ester of a long-chain fatty acid derived from the
oils listed above, which conform to American Society for
Testing and Materials (ASTM) D6751 specifications for use in
diesel engines. Typically, biodiesel is produced by mixing a lipid
with an alcohol (usually methanol) and a basic catalyst (usually
sodium hydroxide, 85% KOH) and then heating to
approximately 70 °C (20 psi) for several hours in a process
called transesterification. This process bonds the methanol to
the oils to produce the monoalkyl esters.7,17,19
10. Alternative Biodiesel Processes. Stages of the
standard process used to produce biodiesel, described in the
previous section, have been studied to improve the overall
process. Following are two examples of process optimization,
which when combined with the lipid oil from algae, can
contribute to an environmentally friendly fuel source.
One process improvement uses the enzyme lipase to
eliminate the need for heating the oil in the transesterification
process.78−80
Researchers have identified that lipase made from
the fungus Metarhizium anisopliae and two Gram-negative
bacteria, Aspergillus oryzae (and A. niger) and Chromobacterium
viscosum, can cause transesterification at room temper-
ature.78−80
This cuts the energy expenditure of biodiesel
production, making the process more energy efficient and less
sensitive to process problems than the standard process.81
Another possible process optimization effort involves using
ethanol instead of methanol in the transesterification process.
Methanol, a component often used in the production of
biodiesel, is highly toxic. If ignited it burns invisibly and can be
absorbed through the skin, making the risk of exposure and
cleanup a serious problem.81
Methanol is also often recovered
from finished biodiesel for reuse. Using ethanol instead allows
biodiesel fuel production entirely from renewable resources.
The use of ethanol has advantages in vehicle emissions and in
controlling microbial growth in storage containers. The storage
of organic products such as petroleum-derived diesel, and
especially biodiesel, can be problematic because organic
products are susceptible to microbial growth when in the
presence of water. The accumulation of water, storage tank
slime, and sediment can harm an engine by clogging fuel filters
and fuel injectors and can increase emissions by affecting
engine performance.78−80
Biodiesel that is combined with
ethanol for the transesterification process or as a fuel additive
can be used both as a component of a fuel blend (such as E10
gasoline) and as a biocide. A biocide can be any chemical that
kills bacteria and mold growing in solution or on fuel tank
surfaces without interfering with the combustion of fuel or the
operation of the engine. Thus, the use of ethanol can control
the problem of microbial contaminants while in storage and
make the biodiesel fuel production process reliant on a
renewable resource. While ethanol has distinct advantages in
biodiesel production, it has not been used or studied as
extensively as has methanol.81
11. Bioethanol. Cyanobacteria (blue-green algae), as
mentioned above in the discussion of process extraction, have
been studied to genetically enhance favorable traits. These algae
are made up of autotrophic prokaryotes; they lack a cell nucleus
and membrane-bound organelles. Deng and Coleman (1999)82
genetically modified these algae to create a pathway for carbon
utilization resulting in the direct generation of ethanol. The
coding for ethanol synthesis from the bacterium Zymomonas
mobiliz was cloned into a vector and then used to transform the
cyanobacterium Synechococcus sp.82
The GMO form of
cyanobacteria directly synthesized ethanol, which diffused
from the cells into the culture medium and the airspace
above it. The growth requirements of this GMO form of
cyanobacteria are light, CO2, and inorganic nutrients such as
that found in wastewater.59,60,82,83
Ongoing research aims to increase ethanol yields or optimize
processes similar to that used by Deng and Coleman (1999).82
Means to improve ethanol production include (1) further
genetic modification; (2) manipulation of the growth
conditions to lower the nutrient concentrations with the
mature growth of cells; and (3) development of more efficient
ethanol capture techniques, such as sequestering technologies,
within the mixture of growth medium and gaseous headspace.
Industrial efforts to produce bioethanol by using photo-
autotrophic organisms in PBRs are underway by Algenol
Biofuels in cooperation with Dow Chemical Company, the
Linde Group, the National Renewable Energy Laboratory
(NREL), the Georgia Institute of Technology, and Membrane
Technology and Research, Inc.84
12. Hydrogen Fuel. In addition to the algae-derived
biofuels already mentioned, various petroleum-like products
and end products can be generated from microalgae. An
additional biofuel, for example, comes from the microalga
Chlamydomonas reinhardtii, which has been demonstrated to
grow in the laboratory to produce hydrogen.30,85
While in a
sulfur deprivation stage, Chlamydomonas reinhardtii stops
producing oxygen and switches to the production of hydro-
7077

gen.30,85
Cladophora fracta and Chlorella protothecoides were
also studied for biofuel production by Demirbas.86
The
generation of hydrogen was shown to be dependent on the
growth media composition, culture conditions, and PBR
design.86
Hydrogen can be used to produce heat, electricity,
or power (via fuel cells) for transportation.
13. Commercial Interests. Worldwide commercial
applications of algae are vast and many products have been
developed. However, the current focus of industrial expansion
has shifted from food-related products to fuel as market forces
emphasize the search for renewable fuels.87
Commercial
interests have created industries with a wide range of products
using many forms of microalgae. One industry, Cyanotech
Corporation based in Kona, HI, for example, uses Chlorella sp.
for nutrition and health products.87
More than 70 other
companies worldwide manufacture Chlorella sp. for health food
purposes. Another example, the Taiwan Chlorella Manufactur-
ing Company, produces 400 tons of dry Chlorella sp. algal
biomass per year.42
Spirulina (Arthrospira) is another algae
often produced for human nutrition due to its high protein
content, health benefits, and overall nutritional value.42
The majority of commercial growth processes of algae use
varieties of open ponds. These commercial facilities are located
in lower latitudes where temperature, climate, and solar
radiance are favorable for algae growth. Some of the primary
commercial algae producers are described below.
Novozymes is an international leader in enzyme and
pharmaceutical production technology and supplies over half
the enzymes used to produce bioethanol in the United States.88
Novozymes employs GMO cloning techniques and gene
expression systems to manufacture enzymes for use in industrial
biofuel generation.88
Additionally, Novozymes assists compa-
nies in replacing process constituents with less environmentally
adverse process constituents.88
As discussed above in the section on Heterotrophic Algae
Respiration and Fermentation, Solazyme employs a hetero-
trophic method to produce a lipid byproduct that is converted
into biodiesel. Solazyme was the first algae manufacturer to be
approved for algae jet fuel production by ASTM.89,90
Solazyme
had a commercial plant by 2010. In 2009, it sold 20 000 gallons
(at a cost of $8.5 million for 20 000 gallons or $425/gallon) of
algae fuel to the U.S. Navy. In 2010 it received another
purchase for 150 000 gallons (at a cost of $10 million for 150
000 gallons or $67/gallon). The initial cost of research and
development was not applied to the second purchase.89,90
Whether the price of Solazyme biodiesel fuel is $425 or $67 per
gallon, this company has demonstrated the ability to deliver a
product as contracted.
Based in San Diego, CA, Sapphire Energy is associated with
Linde Industries. Sapphire Energy operates a facility in New
Mexico that uses an open pond system with CO2 injection that
produces a lipid-like petroleum.4
Sapphire Energy’s goals are to
produce 1 million gallons of algae-derived biodiesel and jet fuel
by 2011, 100 million gallons by 2018, and 1 billion gallons by
2025.4
Synthetic Genomics, Inc. (SGI) received $600 million in
2009 from Exxon for research and development. SGI has
developed a GMO strain of algae that can produce a petroleum-
like lipid.91
Algenol Biofuels is using a GMO form of cyanobacteria (a
form of blue-green microalgae grown in an autotrophic process
within PBRs) to directly synthesize ethanol. The ethanol
diffuses through the microalgae cell wall into the culture
medium and the confined airspace of the PBR. The
cyanobacteria require light, CO2, and inorganic elements and
are being grown in combination with municipal wastewater and
commercial CO2 effluent integrated in a pilot-scale biorefi-
nery.82
The U.S. Department of Energy (DOE) has selected
Algenol for a $25 million grant to support this work. Algenol is
also working in cooperation with Dow Chemical Company, the
Linde Group, the National Renewable Energy Laboratory
(NREL), the Georgia Institute of Technology, and Membrane
Technology and Research, Inc.84
Cellana (formerly HR BioPetroleum, Inc., (HRBP)) was
founded in Hawaii in 2004 to produce feedstocks for biofuels,
personal care products, nutritional oils, renewable chemicals,
and aquaculture and livestock feed. Cellana’s patented Alduo
technology (a combination PBR/PRP autotrophic process)
uses industrial emissions of CO2, sunlight, and a non-GMO
strain of microalgae. HRBP and Royal Dutch Shell PLC formed
Cellana, which operates a six-acre demonstration facility to
produce marine algae and harvest oil for conversion into
biofuel.92
Heliae Development, LLC, produces multiple algae strains
and multiproduct refining including algae-derived jet fuels at its
pilot facility in Gilbert, AZ. Azmark Aero Systems has tested
algae-derived jet fuels in small gas turbine engines for use in
military unmanned aerial vehicles. Heliae currently uses
autotrophic non-GMO algal strains in PBRs while using CO2
and wastewater.93
This process using non-GMO algal strains
has been developed in cooperation with Arizona State
University to allow growth in a range of climates. Heliae’s
proprietary PBR is designed to maximize efficiency, production
consistency, and per-acre yields.93
14. Economics of Algae. The fluctuating price of
petroleum continues to set the economic standard that all
biofuels must meet to be competitive. Microalgae lipid
production has the greatest potential for the production of
renewable fuels. Although many processes (with theoretical
costs) use various forms of microalgae, information on algal
biofuel production costs is limited to biodiesel. Additionally,
the production costs discussed below do not have the benefit of
economics of scale. Until an established plant is able to produce
a minimum of 1 million gallons per year of biofuel, the cost
projections will be based on assumptions. While useful, even
the best assumptions are likely to be inaccurate. The ultimate
costs, both economic and resource (land, water, and air) costs,
of large-scale production are largely unknown.
Biodiesel production can be achieved by both heterotrophic
and autotrophic processes. The cost of feedstock or carbon
source (carbohydrate) in the heterotrophic process accounts
for 60−75% of the total cost of biodiesel.6,48,49,91
The most
recent price of biodiesel fuel produced and delivered by
Solazyme was $67 per gallon. Although not competitive,
Solazyme achieved a notable milestone in this rapidly
developing market.89,90
Chisti7
compared PBR and PRP facilities, which are detailed
in Table 3. Both example techniques produce 100 tons of
biomass and consume 183 333 kg of atmospheric CO2. Both
techniques are compared with optimal productivity and process
concentrations that have been documented in actual large-scale
PBRs and PRPs. The PBR technique for oil yield illustrated in
the table has been shown to achieve a 38% greater oil yield per
hectare compared with PRP techniques. Both PBR and PRP
techniques are used extensively in commercial opera-
tions.7,42,53,54,66,94,95
7078

As mentioned above, recovery of the microalgal biomass
from the culture broth is the necessary first step for using the
target product. The techniques for biomass separation are
filtration, centrifugation, and other means.55
The cost of
biomass separation can be significant and is dependent on the
technique employed. PBR recovery costs are typically less than
PRP costs due to the higher biomass concentration (nearly 30
times greater than PRP).7
The cost of producing a kilogram of
microalgal biomass is estimated to be approximately $2.95 for
PBR and $3.80 for PRP.55,96
If the production scale is increased
to an annual biomass capacity of 10 000 tons, the biomass per
kilogram production cost decreases to approximately $0.47 for
PBR and $0.60 for PRP.
With a conservative assumption of 30% oil extraction
efficiency by weight of biomass, the cost of a liter of extracted
oil would be $1.40 for PBR ($5.30/gal) and $1.81 for PRP
($6.85/gal).7,55,96
The conversion to algae-derived biodiesel,
assuming a standard 66% efficiency, would yield a cost of
$8.03/gal for PBR and $10.38/gal for PRP.
Improvements in growth techniques, GMO efficiency and
stability, and process efficiency have continued to evolve since
the values above were current. These improvements will
continue to drive the cost of biodiesel produced from algae oil
closer to being competitive with other sources that are
produced from feedstocks such as palm, soybean, canola, and
petroleum.
Currently there are no commercial algae plants operating on
a consistent schedule for the purpose of producing biofuel.
Without a working example and an industry that is willing to
share information on costs and revenues derived, the
hypothetical example given above is the best speculative
estimate available. It is conceivable that locating large scale
algae plants which take advantage of available high nutrient
wastewater and industrial sources of CO2
and waste-heat can
produce biodiesel for half the $8.03/gal price derived above. At
the approximate price of $4/gal algae derived biodiesel would
be competitive with other biodiesel feedstocks and petroleum
derived diesel. This hypothetical scenario would have the
additional benefits of reducing wastewater nutrient loads,
minimizing the plant water demands, and sequestering CO2
.
Additionally, the value of the nonlipid algae solid residue
cannot be ignored. Depending on the actual content of the
species utilized, high levels of carbohydrate could be used for
ethanol generation and a high protein content could be used for
animal feed.
15. Risk Association. Depending on the algae organism
and the process used, the constituents of the algae biomass and
process stream can vary. A typical process might involve
microorganisms such as bacteria, mold, and yeast, including
GMOs, and a wide variety of ingredients used to generate the
algae and convert this biomass into a desired end product.1,2,74
The contents could also have potential human health risks such
as those from infection (bacteria, mold, yeast, and GMOs) and
exposure to allergens, toxins, carcinogens (endotoxins,
mycotoxins, proteins, and organic and inorganic chemicals),
antibiotics (used to prevent unwanted biological growth),
enzymes (used to hydrolyze cellulose), chemicals (process
additives), and acidic and caustic materials (used to hydrolyze
cellulose).1,2
The biofuel production industry is composed of many
companies, each of which has adopted its own process and, for
many, its own GMO form of algae. Each proprietary process
design, and the reagents used (e.g., microorganisms, enzymes,
chemicals), will determine the quantity and nature of waste
produced. The various biological processes will amplify the
microbial populations (including GMO varieties), algae, toxins,
and enzymes that may be potentially hazardous to the
environment and individuals. Each process could contain
constituents that are potentially pathogenic, toxic, infective, or
allergenic and that are of concern for affecting native microbial
populations and, consequently, ecosystem balance. It is unclear
what the impacts of release of these materials might be, but
without a more complete understanding of the composition
and amounts produced by the various processes, it is impossible
to adequately estimate the risk associated with these materials.
Potential human and environmental risks exist in association
with the numerous forms of GMO algae that are being
developed for biofuel generation. The various risks are
toxigenicity (from known and unknown GMO toxins),
allergenic responses (from proteins and organic and inorganic
chemicals), and unknown environmental effects that could
potentially cause the unintended transfer of transgenes or cause
the loss of flora and fauna biodiversity. An evaluation
methodology is needed to better understand the GMO effects
and their associated risks to the environment.
16. Toxicological Impacts. Algae populations can be
affected by increased waterborne nutrient load caused by
farming, growing populations, land use development, and
trends causing increased environmental stress to wetlands and
marshes. Freshwater algae, marine algae, and cyanobacteria all
produce toxins. These toxins can induce dermatitis, neuro-
logical disruptions, and hepatotoxicity or liver failure.46,97,98
Anthropogenic factors such as point and nonpoint source
discharges into waterways can cause increased nutrient levels in
marine and limnic environments triggering algae blooms and
negatively impacting biodiversity with increased toxins and
decreased dissolved oxygen levels.97,99−101
Commonly referred
to as fish kills, the effects can be widespread and environ-
mentally detrimental. Increased incidents of toxic algae are
being documented in more localities and at greater frequency
and magnitude.102
Table 3. Comparison of Photobioreactor and Raceway
Production Methods7
variable PBR PRP
annual biomass
production (kg)
100 000 100 000
volumetric
productivity (kg
m−3
d−1
)
1.535 0.117
areal productivity
(kg m−2
d−1
)
0.048a
0.035b
0.072c
biomass
concentration in
broth (kg m−3
)
4.00 0.14
dilution rate (d−1
) 0.384 0.250
area needed (m2
) 5681 7828
oil yield (m3
ha−1
) 136.9d
99.4d
58.7e
42.6e
annual CO2
consumption (kg)
183 333 183 333
system geometry 132 parallel tubes/unit; 80 m
long tubes; 0.06 m tube
diameter
978 m2
/pond; 12 m
wide, 82 m long, 0.30
m deep
number of units 6 8
a
Based on facility area. b
Based on actual pond area. c
Based on
projected area of photobioreactor tubes. d
Based on 70% by weight oil
in biomass. e
Based on 30% by weight oil in biomass.
7079

Algae bloom formations are known to create high
concentrations of toxins, which can be controlled by limited
water volume, warm water temperature, high nutrient
concentrations, high pH, low CO2, and the low nutrient uptake
rate demonstrated by zooplankton.103
Numerous lakes, rivers,
sounds, and oceans have experienced pollution from algal
blooms that generate many toxins such as peptide hepatotoxin
microcystin-LR. Human and animal exposures usually occur
through drinking water ingestion, recreational activities,
absorption by contact, or inhalation. Knowledge of the effects
of many toxins of algal origin on humans and animals is limited,
and knowledge of the effects of GMO microalgae is
nonexistent.98
Marine microalgae can cause many human illnesses linked to
the consumption of seafood and the inhalation of contaminated
aerosolized toxins. They have also been responsible for the
massive die-off of fish, shellfish, and marine vertebrates, as well
as the corresponding mortality in seabirds, marine mammals,
and other animals.104
Marine microalgae produce toxins that
cause 60 000 human intoxications (a physiological state of
impairment) per year worldwide, with a mortality rate of 1.5%
(or 900 fatalities).104
Most fatalities are caused by ingestion of
seafood containing saxitoxins, tetrodotoxins, and in rare cases,
ciguatera and domoic acid.71,105−107
Only acute intoxications
have been studied for their toxicological or medical effects,
while chronic or low-concentration exposures have
not.71,105−107
Marine toxins are produced by two algal groups, dino-
flagellates and diatoms. Of the 3000 species of dinoflagellates
and diatoms, approximately 2%, or 60−80 species, are known
to be toxic.71,105−108
The majority of these toxins are
temperature-stable neurotoxins, which eliminates cooking as a
control measure.
In addition to human intoxications, marine toxins cause
deaths to other forms of marine life and wildlife that are
dependent on the aquatic food chain. Marine biotoxins, such as
diatoms and red algae (Chondria spp.), are routinely monitored
for toxins, including paralytic, neurotoxic, diarrhetic, and
amnesic shellfish toxins, as well as compounds such as
yessotoxins, specifically pectenotoxin and gymnodimine.
Monitoring of algae blooms and other harmful algae is
constantly reviewed in the light of new research that
incorporates local knowledge of oceanographic and climatic
conditions. Increased awareness, monitoring, surveillance, and
identification of toxic algae blooms are the only means of
control or avoidance.109−112
17. Pollution Control and Remediation. Algae can have
both positive and negative environmental impacts. Among the
positive effects of algae are removal of excessive amounts of
nitrogen (N), phosphorus (P), and sulfur (S) from municipal
and agricultural wastewater and the sequestration of CO2 from
stack emissions. A potential negative impact is the release of
toxigenic, carcinogenic, and allergenic algal products as well as
viable organisms, including GMOs, into the environment.
The biomass of microalgae contains approximately 50%
carbon, which is obtained from the atmosphere or from
commercial sources of CO2. Carbon sequestration from
industrial sources has been demonstrated to increase algae
yield.87,112−114
The wide range of algae growth requirements means that not
all algae are readily adaptable to the conditions within a
wastewater treatment plant. Research performed by Bhatnagar
and Bhatnagar demonstrated that Chlorella minutissima has a
positive impact in municipal wastewater remediation.115,116
In
this study, C. minutissima removed 75% of the biochemical
oxygen demand (BOD5), 41% N, 30% P, and 30% S.
A benchtop study performed by Woertz et al.117
examined
algae lipid productivity using municipal and agricultural
wastewater. The municipal wastewater stream was populated
by the algae genera Chlorella, Micractinium, and Actinastrum,
and the lipid contents ranged from 9.7 mg L−1
day−1
(with the
addition of air sparge and a 3-day hydraulic residence time
[HRT]) to 24 mg L−1
day−1
(with the addition of CO2 sparge
and a 3-day HRT). Lipid production using dairy wastewater
was populated by the algae genera Scenedesmus, Micractinium,
Chlorella, and Actinastrum and demonstrated a maximum value
of 17 mg L−1
day−1
.117
Although this work is preliminary, the
results indicate a fundamental positive correlation with nutrient
removal and lipid production with the additional improvement
of CO2 uptake.
Bench-top research conducted by Kong et al.67
used
Chlamydomonas reinhardtii in both artificial media and
wastewater (influent, effluent, and concentrate) over a 10 day
period. The amount of algae growth and pH were measured
with the addition of CO2. The experiment demonstrated results
of 0.82 g L−1
day−1
in flask reactors and 2.0 g L−1
day−1
in
PBRs.67
The wastewater contained in flasks exhibited a 42.2−
55.0% removal of N (as NH4) and 12.5−15.4% removal of P
(as PO4). In the PBR, approximately 83.0% of the N and
14.45% of the P were removed from the wastewater.67
The 10
day yield for C. reinhardtii was 25.25% oil in the PBR and 16.6%
in the flask reactors.67
Algae play an integral role in the earth’s carbon cycle, using
many sources of carbon but depending on CO2 as the main
source. Sparging concentrated CO2 emissions (such as those
found in flue gas) into the algal culture can increase the
dissolved CO2 concentration above ambient (0.036%) and
elicit an increase in algae growth.118
Temperature also regulates
cellular metabolic functions that can increase algae production.
The beneficial increase in metabolism caused by increasing
temperature is limited to the point when protein synthesis is
affected.
Chlorella vulgaris was studied by Chinnasamy et al.118
for
optimizing algae growth conditions using wastewater and
increased levels of temperature and CO2. The findings showed
that at a temperature of 30 °C and with an elevated CO2
concentration of 6% algae biomass increased 114% DW (210
μg mL−1
) more than at ambient. However, at CO2
concentrations greater than 6%, Chlorella vulgaris demonstrated
a decrease in growth rate with decreasing pH levels.118
The
increase in biomass was observed for protein and carbohydrate,
whereas the lipid concentration decreased by 5.8%.118
This
benchtop research demonstrates a useful methodology needed
to find the optimal algae growing conditions.
A benchtop study conducted by Francisco et al.119
tested six
strains of microalgae in a PBR employing CO2 sequestration.
Chlorella vulgaris demonstrated the best biomass productivity of
20.1 mg L−1
h−1
and lipid content of 27.0% at 5.3 mg L−1
h−1
for biodiesel production.
Theoretical models published by Pokoo-Aikins et al.9
and
Rosenberg et al.10
use CO2 sequestration as an integral part of
generating algae for biodiesel and ethanol biorefineries,
respectively. Research continues to provide examples of biofuel
generation using wastewater nutrients and CO2 sequestration.
These examples provide a wealth of knowledge to guide
industrial applications. However, the status of current industrial
7080

applications is not routinely made known but rather is treated
as proprietary.
It is difficult to predict the environmental impact of
industrialized algae cultivation. The use of algae-derived
sustainable biofuels such as biodiesel and ethanol rather than
petroleum-based fuels such as gasoline and diesel will have a
very positive effect on air quality.120
When algae production is
also combined with wastewater treatment and CO2 sequestra-
tion, the potential for environmental benefits are great.
18. Promotion Authority. Both the U.S. DOE and the
U.S. Department of Agriculture (USDA) have provided funding
mechanisms for research and development of algae biofuel
production as a means to stimulate commercial involvement.
This section provides some examples of those provisions meant
to initiate commercial applications of algae-derived biofuel
ventures. Except for Solazyme’s site in Riverside, PA, all of
these examples are located in southern latitudes, presumably to
take advantage of the moderate climate, temperature, and solar
radiance.
DOE has announced three grants totaling $24 million for
three research groups addressing specific projects on algae-
based biofuels.121
These DOE-funded projects are as follows:
• Sustainable Algal Biofuels Consortium of Mesa, AZ, has
received a DOE grant of $6 million.121
The project is
directed by Arizona State University and will focus on
testing the acceptability and comparing algal biofuels as
replacements for petroleum-based fuels.121
Biological
pathways using algae to generate biofuels are also being
studied.121,122
• The Consortium for Algal Biofuels Commercialization is
directed by the University of California, San Diego, and
has received a $9 million DOE grant.121
This work
involves developing biofuel feedstocks, nutrient use,
process stream recycling, and genetic enhancement for
culture optimization and process stabilization.121
• Cellana, LLC Consortium of Kailua-Kona, HI, is directed
by Cellana, LLC, and has received a $9 million DOE
grant.121
This work involves developing enhanced-scale
biofuel production of marine algae in seawater.121
Additionally, research and development of feedstock
byproduct use for aquaculture is being conducted.121
To assist commercial algae biorefinery projects through the
construction and operation of pilot-scale demonstrations, three
industries were selected to receive nearly $100 million in grants
from USDA’s American Recovery and Reinvestment Act.123
Additionally, the Biorefinery Assistance Program, which is part
of the 2008 Farm Bill, provides funds for technology
development and guarantees loans to develop, construct, and
retrofit working commercial-scale biorefineries.123,124
The three
industries receiving grants and loan guarantees are as follows:
• Algenol Biofuels, Inc., of Freeport, TX, received a DOE
grant of $25 000 000 and $33 915 478 in nonfederal
funding. Algenol will generate ethanol directly from an
autotrophic microalgae process using carbon dioxide and
seawater. This pilot-scale facility will have the capacity to
produce 100 000 gallons of fuel-grade ethanol per
year.123,125
• Solazyme, Inc., of Riverside, PA, received a DOE grant of
$21 765 738 and $3 857 111 in nonfederal funding.
Solazyme will investigate the economic feasibility of
large-scale algae biofuel production.123,125
• Sapphire Energy, Inc., of Columbus, NM, received a
DOE grant of $50 000 000 and $85 064 206 in non-
federal funding. Sapphire will focus research on pond
production of algae-derived biofuels.123,125
In March 2011, USDA, Rural Business-Cooperative Service,
Rural Utilities Service, announced that $85 million in grant
funding was available to biofuel producers.126
The funding is to
“support and ensure expanding production of advanced
biofuels.”126
Applications were taken and awards are expected
to be announced.
19. Regulatory Authority. The USDA regulates GMOs
from the standpoint of preventing the spread of pests, weeds,
and diseases under the Federal Plant Pest Act (FPPA). USDA
also regulates the spread of new varieties of feedstock whether
they are developed by selection or hybridization, or are
genetically modified. Crops that are bioengineered for pest
resistance could have a number of advantages, such as increased
yield and reduced or eliminated use of insecticides.127
Hundreds of field trials of GMO plants are now being carried
out each year with only researcher notification, as is required by
the USDA.127
The U.S. Food and Drug Administration (FDA) has the
authority to regulate manufactured products containing GMOs.
Examples of FDA product responsibility are the safety of food,
food additives, livestock feed, and medical products. Few
products, however, have been identified as requiring agency
approval under the Food, Drug and Cosmetic Act (FDCA). “If
the gene-modified organism expresses a pesticide or functions
as a pesticide, the Environmental Protection Agency (EPA)
regulates it under the Federal Insecticide, Fungicide and
Rodenticide Act (FIFRA).”101
Additionally, under the Toxic
Substances Control Act (TSCA), EPA also controls GMOs that
have no pesticide functions. An example is a bacterium
engineered to produce ethanol from residue carbohydrate.127
The discharge of pollutants into surface waters of the United
States is regulated by the Clean Water Act, specifically through
the National Pollutant Discharge Elimination System (NPDES)
permit program.101,128
The regulatory distinction of monitoring, treating, and
ultimately controlling GMO discharges by NPDES permitting
is unclear. Beyond nutrient load, GMOs contained in NPDES
discharges have the potential to impact drinking water supplies
as well as the environment at large. Genetically modified or
enhanced organisms could possess characteristics such as fast
growth rate or tolerance to contaminants that would threaten
the stability of natural ecosystems. When a new GMO is
introduced, there is a need to be sure of the safety related to
possible exposure. The scope of any GMO study ideally will
cover the potential for any unforeseen problems that its
introduction could cause.62,128
The Energy Independence and Security Act of 2007 (Pub. L.
110−140) was created by an Act of Congress with the stated
purpose “to move the United States toward greater energy
independence and security, to increase the production of clean
renewable fuels, to protect consumers, to increase the efficiency
of products, buildings, and vehicles, to promote research on and
deploy greenhouse gas capture and storage options, and to
improve the energy performance of the Federal Govern-
ment”.129
EISA set forth improved vehicle fuel economy
targets, biofuels production standards, and energy savings
standards, and specified research and development of solar
energy, geothermal energy, and marine and hydrokinetic
7081

renewable energy technologies and federal research on carbon
sequestration technologies.129
II. SUMMARY AND FUTURE CONTRIBUTION OF
ALGAE
The process of generating biofuel from algae involves the
growth, concentration, separation, and conversion of micro-
algae biomass, some of which can be genetically altered. After
separating the desired biofuel product or products from the
microalgae biomass, a significant portion of byproduct remains.
It is important that the remaining byproducts have a useful and
safe purpose for the economic feasibility and environmental
sustainability of the process.
If ethanol is a desired product from algae carbohydrate, the
process can also involve bacteria, mold, and yeast, some of
which may be genetically modified.128
The waste streams may
include these microorganisms as well as the biological toxins,
allergens, and carcinogens produced by these microorganisms;
antibiotics; enzymes; chemicals (e.g., wastewater high in
nutrients, BOD); as well as acids and bases. Exposure to
GMOs carries possible human and environmental health risks.
Risks to humans include toxigenicity and allergenic responses.
Environmental impacts of GMOs include their potential to
cause the unintended transfer of transgenes or to cause the loss
of flora and fauna biodiversity. An evaluation methodology
should be employed to better understand the content of algae
production and waste streams and the associated risks to
humans and the environment.
As a sustainable source of energy, algae and the feedstocks
they produce have great potential to meet the demands of
replacing petroleum-based fuels. The versatility of algae to
produce lipids, carbohydrates, and protein will be needed to
create multiple products in multiple markets to successfully
satisfy economic demand. Currently, biotechnology firms and
the algae industry are focused on producing relatively low
volumes of high-value products such as pharmaceuticals or
nutritional supplements. These same industries must refocus on
high volumes of biofuel production at low, competitive prices,
as well as using byproducts such as the protein for distiller’s
grains and carbohydrates for ethanol.130
Postextraction by-
products must be used efficiently and completely.
Algae-derived biofuel will directly impact the generation of
transportation fuels (biodiesel, ethanol, and petroleum), and as
part of the future of renewable fuel it will also impact many
environmental and economic resources. Examples of these
impacts are the treatment of wastewater; capture of carbon
dioxide from power plants; production of human and animal
food, pharmaceuticals, cosmetics, and organic fertilizers;
aquaculture; and soil nutrient recovery. Ultimately, the need
to decrease fossil fuel dependence makes it imperative that
algae and algae-derived products are safe to humans and the
environment. The rapid commercial expansion of the algae
biofuels industry is an excellent example of sustainable product
development with dramatic future potential for contributions to
fuel supplies, yet many questions regarding algae production
remain unanswered. The state of knowledge regarding the
potential environmental impact of the production of algae and
algae-derived biofuels continues to be incomplete, fragmented,
and largely obscured by proprietary concerns. This knowledge
is, however, changing rapidly, facilitated by research and
industry and driven by economics.
Commercialization of the production of algae derived
biofuels as part of the overall biofuel industry will have a
profound future impact on society. Waste products that are
currently discharged into the environment as contaminants will
be utilized to produce much needed renewable energy sources.
Now is the time to initiate the development of an algae industry
evaluation methodology that allows for the advancement of
knowledge and evaluation tools for authorities to best
understand the potential implications.
■ AUTHOR INFORMATION
Corresponding Author
*Phone: 919-541-7981; fax: 919-541-2157; e-mail: menetrez.
marc@epa.gov.
Notes
The authors declare no competing financial interest.
■ REFERENCES
(1) Evangelista, V., Barsanti, L., Frassanito, A. M., Passarelli, V.,
Gualieri, P. Algal toxins: Nature, occurrence, effect and detection . In
Proceedings of the NATO Advanced Study Institute on Sensor Systems for
Biological Threats; The Algal Toxins Case: Pisa, Italy, 2008; ISBN: 978-
1-4020-8479-9.
(2) Graham, L. E.; Graham, J. E.; Wilcox, L. W. Algae, 2nd ed.;
Benjamin-Cummings Publishing: Menlo Park, CA, 2008; ISBN:
0321559657.
(3) Li, X.; Xu, H.; Wu, Q. Large-scale biodiesel production from
microalga Chlorella protothecoides through heterotrophic cultivation in
bioreactors. Biotechnol. Bioeng. 2007, 98, 764−771.
(4) A. France-Presse, Sapphire Energy, Linde unveil CO2 algae-to-
fuel deal: German industrial gas giant will deliver carbon dioxide,
Industry Week, 2011. http://www.industryweek.com/articles/
sapphire_energy_linde_unveil_cosub2/sub_algae-to-fuel_deal_
24600.aspx?ShowAll=1&SectionID=36 (accessed December 14,
2011).
(5) Hu, Q.; Sommerfeld, M.; Jarvis, E.; Ghirardi, M.; Posewitz, M.;
Seibert, M.; Darzins, A. Microalgal triacylglycerols as feedstocks for
biofuel production: Perspectives and advances. Plant J. 2008, 54, 621−
639.
(6) Hughes, E.; Benemann, J. R. Biological fossil CO2 mitigation.
Energy Convers. Manage. 1997, 38, S467−S473.
(7) Chisti, Y. Biodiesel from microalgae. Biotechnol Adv. 2007, 25,
294−306.
(8) Hu, Q., Zhang, C., Sommerfeld, M. Biodiesel from algae: Lessons
learned over the past 60 years and future perspectives. In Annual
Meeting of the Phycological Society of America, Juneau, AK, July 7−12,
2006, pp. 40−41.
(9) Pokoo-Aikins, G.; Nadim, A.; El-Halwagi, M.; Mahalec, V. Design
and analysis of biodiesel production from algae grown through carbon
sequestration. Clean Technol. Environ. Policy 2010, 12, 239−254.
(10) Rosenberg, J. N.; Mathias, A.; Korth, K.; Betenbaugh, M. J.;
Oyler, G. A. Microalgal biomass production and carbon dioxide
sequestration from an integrated ethanol biorefinery in Iowa: A
technical appraisal and economic feasibility evaluation. Biomass
Bioenergy 2011, 35, 3865−3876.
(11) Lehr, F. Posten, Closed photo-bioreactors as tools for biofuel
production. Curr. Opin. Biotechnol. 2009, 20, 280−285.
(12) Shen, Y.; Pei, Z.; Yuan, W.; Mao, E. Effect of nitrogen and
extraction method on algae lipid yield. Int. J. Agric. Biol. Eng. 2009, 2
(1), 51−57.
(13) Andersen, T.; Andersen, F. O. Effects of CO2 concentration on
growth of filamentous algae and Littorella uniflora in a Danish
softwater lake. Aquat. Bot. 2006, 84, 267−271.
(14) Hanagata, N.; Takeuchi, T.; Fukuju, Y.; Barnes, D. J.; Karube, I.
Tolerance of microalgae to high CO2 and high temperature.
Phytochemistry 1992, 31, 3345−3348.
(15) Adams, J. M.; Gallagher, J. A.; Donnison, I. S. Fermentation
study on Saccharina latissima for bioethanol production considering
variable pre-treatments. J. Appl. Phycol. 2009, 21, 569−574.
7082

(16) Becker. Micro-algae as a source of protein. Biotechnol. Adv. 2007,
25, 207−210.
(17) Gouveia, L.; Marques, A. E.; da Silva, T. L.; Reis, A. Neochloris
oleabundans UTEX #1185: A suitable renewable lipid source for
biofuel production. J. Ind. Microbiol. Biotechnol. 2009, 36, 821−826.
(18) Coppola, F.; Simonciniand, E.; Pulselli, R. M. Bioethanol
potentials from marine residual biomass: An energy evaluation. Energy
Environ. 2009, 122, 379−387, 0013-936X.
(19) Meng, X.; Yang, J.; Xu, X.; Zhang, L.; Nie, Q.; Xian, M.
Biodiesel production from oleaginous microorganisms. Renew. Energy
2009, 34, 1−5.
(20) Li, Q.; Du, W.; Liu, D. Perspectives of microbial oils for
biodiesel production. Appl. Microbiol. Biotechnol. 2008, 80, 749−756.
(21) Li, Y.; Horsman, M.; Wang, B.; Wu, N.; Lan, C. Q. Effects of
nitrogen sources on cell growth and lipid accumulation of green alga
Neochloris oleoabundans. Appl. Microbiol. Biotechnol. 2008, 81, 629−
636.
(22) Li, X.; Hu, H. Y.; Gan, K.; Yang, J. Growth and nutrient removal
properties of a freshwater microalga Scenedesmus sp. LX1 under
different kinds of nitrogen sources. Ecol. Eng. 2010, 36, 379−381.
(23) Li, Y.; Han, D.; Sommerfeld, M.; Hu, Q. Photosynthetic carbon
partitioning and lipid production in the oleaginous microalga
Pseudochlorococcum sp. (Chlorophyceae) under nitrogen-limited con-
ditions. Bioresour. Technol. 2011, 102, 123−129.
(24) Liang, Y.; Cui, Y.; Trushenski, J.; Blackburn, J. W. Converting
crude glycerol derived from yellow grease to lipids through yeast
fermentation. Bioresour. Technol. 2010, 101, 7581−7586.
(25) Briggs, M. Widescale Biodiesel Production from Algae; University
of New Hampshire Biodiesel Group, 2004.
(26) Laurens, L. M. L.; Wolfrum, E. J. Feasibility of spectroscopic
characterization of algal lipids: Chemometric correlation of NIR and
FTIR spectra with exogenous lipids in algal biomass. Bioenergy Res.
2011, 4, 22−35.
(27) Reitan, K. I.; Rainuzzo, J. R.; Olsen, Y. Effect of nutrient
limitation on fatty acid and lipid content of marine microalgae. J.
Phycol. 1994, 30, 972−979.
(28) Renaud, S. M.; Thinh, L. V.; Lambrinidis, G.; Parry, D. L. Effect
of temperature on growth, chemical composition and fatty acid
composition of tropical Australian microalgae grown in batch cultures.
Aquaculture 2002, 211, 195−214.
(29) Gladue, R. M.; Maxey, J. E. Microalgal feeds for aquaculture. J.
Appl. Phycol. 1994, 6, 131−141.
(30) Beer, L. L.; Boyd, E. S.; Peters, J. W.; Posewitz, M. C.
Engineering algae for biohydrogen and biofuel production. Curr. Opin.
Biotechnol. 2009, 20, 264−271.
(31) Clarens, A. F.; Nassau, H.; Resurreccion, E. P.; White, M. A.;
Colosi, L. M. Environmental impacts of algae-derived biodiesel and
bioelectricity for transportation. Environ. Sci. Technol. 2011, 45 (17),
7554−7560.
(32) Kübler, J. E.; Johnston, A. M.; Raven, J. A. The effects of
reduced and elevated CO2 and O2 on the seaweed Lomentaria
articulata. Plant Cell Environ. 1999, 22, 1303−1310.
(33) Logothetis, K.; Dakanali, S.; Ioannidis, N.; Kotzabasis, K. The
impact of high CO2 concentrations on the structure and function of
the photosynthetic apparatus and the role of polyamines. J. Plant
Physiol. 2004, 161, 715−724.
(34) Tisserat, B. Influence of ultra-high carbon dioxide levels on
growth and morphogenesis of Lamiaceae species in soil. J. Herbs Spices
Med. Plants 2002, 9, 81−89.
(35) González-Fernández, C.; Molinuevo-Salces, B.; García-
González, M. C. Nitrogen transformations under different conditions
in open ponds by means of microalgae−bacteria consortium treating
pig slurry. Bioresour. Technol. 2011, 102, 960−966.
(36) Venkata Mohan, S.; Mohanakrishna, G.; Raghuvulu, S. V.;
Sarma, P. N. Enhancing biohydrogen production from chemical
wastewater treatment in anaerobic sequencing batch biofilm reactor
(AnSBBR) by bioaugmenting with selectively enriched kanamycin
resistant anaerobic mixed consortia. Int. J. Hydrogen Energy 2007, 32,
3284−3292.
(37) Venkata Mohan, S.; Bhaskar, Y. B.; Krishna, T. M.;
Chandrasekhara Rao, N.; Lalit Babu, V.; Sarma, P. N. Biohydrogen
production from chemical wastewater as substrate by selectively
enriched anaerobic mixed consortia: Influence of fermentation pH and
substrate composition. Int. J. Hydrogen Energy 2007, 32, 2286−2295.
(38) Sukenik, A.; Levy, R. S.; Levy, Y.; Falkowski, P. G.; Dubinsky, Z.
Optimizing algal biomass production in an outdoor pond: A
simulation model. J. Appl. Phycol. 1991, 3, 191−201.
(39) Huntley, M. E.; Redalje, D. G. CO2 mitigation and renewable oil
from photosynthetic microbes: A new appraisal. Mitigation Adaptation
Strat. Global Change 2007, 12, 573−608.
(40) Becker, E. W., Microalgae: Biotechnology and Microbiology;
Cambridge University Press, 1994; ISBN 978-0-521-06113.
(41) Sheehan, J.; Dunahay, T.; Benemann, J.; Roessler, P. A Look
Back at the U.S. Department of Energy’s Aquatic Species Program
Biodiesel from Algae; National Renewable Energy Laboratory (NREL):
Golden, CO, 1998.
(42) Spolaore, P.; Joannis-Cassan, C.; Duran, E.; Isambert, A.
Commercial applications of microalgae. J. Biosci. Bioeng. 2006, 101,
87−96.
(43) Lee, C. G. Calculation of light penetration depth in
photobioreactors. Biotechnol. Bioprocess Eng. 1999, 4, 78−81.
(44) Mussgnug, J. H.; Thomas-Hall, S.; Rupprecht, J.; Foo, A.;
Klassen, V.; McDowall, A.; Schenk, P. M.; Kruse, O.; Hankamer, B.
Engineering photosynthetic light capture: Impacts on improved solar
energy to biomass conversion. Plant Biotechnol. J. 2007, 5, 802−814.
(45) Muller, C.; Reuter, W.; Wehrmeyer, W. Adaptation of the
photosynthetic apparatus of Anacystis nidulans to irradiance and CO2
-
concentration. Bot. Acta 1993, 106, 480−487.
(46) Rapala, J.; Sivonen, K. Assessment of environmental conditions
that favor hepatotoxic and neurotoxic Anabaena spp. strains cultured
under light limitation at different temperatures. Microb. Ecol. 1998, 36,
181−192.
(47) Briassoulis, D.; Panagakis, P.; Chionidis, M.; Tzenos, D.; Lalos,
A.; Tsinos, C.; Berberidis, K.; Jacobsen, A. An experimental helical-
tubular photobioreactor for continuous production of Nannochloropsis
sp. Bioresour. Technol. 2010, 101, 6768−6777.
(48) Borowitzka, M. A. Microalgae for aquaculture: Opportunities
and constraints. J, Appl. Phycol. 1997, 9, 393−401.
(49) Brennan, L.; Owende, P. Biofuels from microalgaeA review of
technologies for production, processing, and extractions of biofuels
and co-products. Renewable Sustainable Energy Rev. 2010, 14, 557−
577.
(50) Kodama, M.; Ikemoto, H.; Miyachi, S. A new species of highly
CO2-tolerant fast growing marine microalga suitable for high density
culture. J. Mar. Biotechnol. 1993, 1, 21−25.
(51) Watanabe, Y.; Ohmura, N.; Saiki, H. Isolation and
determination of cultural characteristics of microalgae which functions
under CO2 enriched atmosphere. Energy Convers. Manage. 1992, 33,
545−552.
(52) Yue, L.; Chen, W. Isolation and determination of cultural
characteristics of a new highly CO2 tolerant fresh water microalgae.
Energy Convers. Manage. 2005, 46, 1868−1876.
(53) Molina Grima, E., Microalgae, mass culture methods. In
Encyclopedia of Bioprocess Technology: Fermentation, Biocatalysis and
BioseparationFlickinger, M. C.; Drew, S. W., Eds.; Wiley, 1999; Vol. 3,
pp 1753−69.
(54) Molina Grima, E.; Acién Fernández, F. G.; García Camacho, F.;
Chisti, Y. Photobioreactors: Light regime, mass transfer, and scaleup. J.
Biotechnol. 1999, 70, 231−247.
(55) Molina Grima, E.; Belarbi, E. H.; Acién Fernández, F. G.; Robles
Medina, A.; Chisti, Y. Recovery of microalgal biomass and metabolites:
Process options and economics. Biotechnol Adv. 2003, 20, 491−515.
(56) Centers for Disease Control and Prevention (CDC). National
Center for Environmental Health, Investigation of Human Health Effects
Associated with Potential Exposure to Genetically Modified Corn; A
Report to the U.S. Food and Drug Administration from the Centers
for Disease Control and Prevention: Atlanta, GA, 2001.
7083

(57) Miraglia, M.; Berdal, K. G.; Brera, C.; Corbisier, P.; Holst-
Jensen, A.; Kok, E. J.; Marvin, H. J. P.; Schimmel, H.; Rentsch, J.; van
Rie, J. P. P. F.; Zagon, J. Detection and traceability of genetically
modified organisms in the food production chain. Food Chem. Toxicol.
2004, 42, 1157−1180.
(58) Sicard, T. E. L. Between development and environment:
Uncertainties of agrofuels. Bull. Sci. Technol. Soc. 2009, 29, 226−235.
(59) U.S. Department of Energy (DOE), Office of Science,
Genomics: GTL Systems Biology for Energy and Environment,
Cellulosic Ethanol: Fuel Ethanol Production, 2008. http://
genomicsgtl.energy.gov (accessed).
(60) Demain, A. L.; Newcomb, M.; Wu, J. H. D. Cellulase, Clostridia,
and ethanol. Microbiol. Mol. Biol, Rev. 2005, 69, 124−154.
(61) Kuiper, H. A.; Kleter, G. A.; Noteborn, H. P.; Kok, E. J.
Assessment of the food safety issues related to genetically modified
foods. Plant J. 2001, 27, 503−528.
(62) Letourneau, D. K.; Robinson, G. S.; Hagen, J. A. Bt crops:
Predicting effects of escaped transgenes on the fitness of wild plants
and their herbivores. Environ. Biosafety Res. 2003, 2, 219−246.
(63) Doucha, J.; Livansky, K. Outdoor open thin-layer microalgal
photobioreactor: Potential productivity. J. Appl. Phycol. 2009, 21, 111−
117.
(64) Gao, K.; Yu, H.; Brown, M. T. Solar PAR and UV radiation
affects the physiology and morphology of the cyanobacterium
Anabaena sp. PCC 7120. J. Photochem. Photobiol. B 2007, 14, 117−
124.
(65) Vasudevan, P. T.; Briggs, M. Biodiesel production-current state
of the art and challenges. J. Ind. Microbiol. Biotechnol. 2008, 35, 421−
430.
(66) Tredici, M. R., Bioreactors. In Encyclopedia of Bioprocess
Technology: Fermentation Biocatalysis and Bioseparation; Flickinger, M.
C., Drew, S. W., Eds.; Wiley, 1999; pp 395−419.
(67) Kong, Q.; Li, L.; Martinez, B.; Chen, P.; Ruan, R. Culture of
microalgae Chlamydomonas reinhardtii in wastewater for biomass
feedstock production. Appl. Biochem. Biotechnol. 2010, 160, 9−18.
(68) Beychok, M. R., Aqueous Wastes from Petroleum and
Petrochemical Plants, 1st ed.; John Wiley and Sons, 1967; LCCN
67019834.
(69) Niederholtmeyer, H.; Wolfstädter, B. T.; Savage, D. F.; Silver, p.
a.; Way, J. C. Engineering cyanobacteria to synthesize and export
hydrophilic products. Appl. Environ. Microbiol. 2010, 76, 3462−3466.
(70) LaMonica, M.; , Solazyme’s algae diesel ready to hit the road,
2008. http://news.cnet.com/8301-11128_3-9965683-54.
html#ixzz1MpaL1xHy (accessed December 20, 2011).
(71) Burkholder, J. M. Implications of harmful microalgae and
heterotrophic dinoflagellates in management of sustainable marine
fisheries. Ecol. Appl. 1998, 8, S37−S62.
(72) Wageningen University, Research on microalgae within
Wageningen UR, 2011. http://www.algae.wur.nl/UK/technologies/
production/heterotrophic_organisms/ (accessed December 20, 2011).
(73) Gao, C.; Zhai, Y.; Ding, Y.; Wu, Q. Application of sweet
sorghum for biodiesel production by heterotrophic microalga Chlorella
protothecoides. Appl. Energy 2010, 87, 756−761.
(74) Demirbas, M. F. Biofuels from algae for sustainable develop-
ment. Appl. Energy 2011, 88, 3473−3480.
(75) Bajpai, D.; Tyagi, V. K. Biodiesel: Source, production,
composition, properties and its benefits. J. Oleo Sci. 2006, 55, 487−
502.
(76) Dismukes, G. C.; Carrieri, D.; Bennette, N.; Ananyev, G. M.;
Posewitz, M. C. Aquatic phototrophs: Efficient alternatives to land-
based crops for biofuels. Curr. Opin. Biotechnol. 2008, 19, 235−240.
(77) Sandefur, H. N.; Matlock, M. D.; Costello, T. A. Seasonal
productivity of a periphytic algal community for biofuel feedstock
generation and nutrient treatment. Ecol. Eng. 2011, 37, 1476−1480.
(78) Adachi, D.; Hama, S.; Numata, T.; Nakashima, K.; Ogino, C.;
Fukuda, H.; Kondo, A. Development of an Aspergillus oryzae whole-
cell biocatalyst coexpressing triglyceride and partial glyceride lipases
for biodiesel production. Bioresour. Technol. 2011, 102, 6723−6729.
(79) Fiametti, K. G.; Sychoski, M. M.; De Cesaro, A.; Furigo, A.;
Bretanha, L. C.; Pereira, C. M. P.; Treichel, H.; de Oliveira, D.;
Oliveira, J. V. Ultrasound irradiation promoted efficient solvent-free
lipase-catalyzed production of mono- and diacylglycerols from olive
oil. Ultrason. Sonochem. 2011, 18, 981−987.
(80) Talukder, M. R.; Das, P.; Shu Fang, T.; Wu, J. C. Enhanced
enzymatic transesterification of palm oil to biodiesel. Biochem. Eng. J.
2011, 55, 119−122.
(81) Lam, M. K.; Lee, K. T. Mixed methanol−ethanol technology to
produce greener biodiesel from waste cooking oil: A breakthrough for
SO4
2−
/SnO2−SiO2 catalyst. Fuel Process. Technol. 2011, 92, 1639−
1645.
(82) Deng, M. D.; Coleman, J. R. Ethanol synthesis by genetic
engineering in cyanobacteria. Appl. Environ. Microbiol. 1999, 65, 523−
528.
(83) Badger, P. C., Ethanol from cellulose: A general review, In
Trends in New Crops and New Uses; Janick, J., Whipkey, A., Eds.; ASHS
Press: Alexandria, VA, 2002; pp 17−21.
(84) Algenol Biofuels, 2011. http://www.algenolbiofuels.com
(accessed December 20, 2011).
(85) Mullner, K.; Happe, T. Biofuel from algae-photobiological
hydrogen production and CO2
-fixation. Int. J. Energy Technol. Policy
2007, 5, 290−295.
(86) Demirbas, M. F. Biofuels from algae for sustainable develop-
ment. Appl. Energy 2011, 88, 3473−3480.
(87) Milledge, Commercial application of microalgae other than as
biofuels: A brief review, Rev. Environ. Sci. Biotechnol., 2011, 10, 31−41.
(88) Phillips, T., Novozymes: A Case Study on Sustainability, 2011.
http://biotech.about.com/od/biotechindailylife/a/Novozymes.htm
(89) Rapier, R., Solazyme CEO Clarifies Costs, Consumer Energy
Report, 2010. http://www.consumerenergyreport.com/2010/10/09/
solazyme-ceo-clarifies-costs/ (accessed December 20, 2011).
(90) BrighterEngergy.org, Solazyme wins 150,000 gallon Navy order
for algal biofuel, Clean Transport News, 2010. http://www.
brighterenergy.org/16288/news/transport/solazyme-wins-150000-
gallon-navy-order-for-algal-biofuel/ (accessed December 20, 2011).
(91) Howell, K., Exxon sinks $600M into algae-based biofuels in
major strategy shift, Energy and Environment, The New York Times.
http://www.nytimes.com/gwire/2009/7/14/14greenwire-exon-sinks-
600m-into-algae-based-biofuels-in-33562.html (accessed December 20,
2011).
(92) Cellana, 2011. http://www.cellana.com (accessed December 20,
2011).
(93) Heliae Development, LLC, , 2011. http://www.heliae.com
(94) Pulz, O. Photobioreactors: Production systems for phototrophic
microorganisms. Appl. Microbiol. Biotechnol. 2001, 57, 287−293.
(95) Terry, K. L.; Raymond, L. P. System design for the autotrophic
production of microalgae. Enzyme Microb. Technol. 1985, 7, 474−487.
(96) Humphreys, K., Jelen’s Cost and Optimization Engineering, 3rd
ed.; McGraw-Hill, 1991.
(97) Kotak, B. G.; Lam, A. K-Y.; Prepas, E. E.; Kenefick, S. L.;
Hrudey, S. E. Variability of the hepatotoxin microcystin-Lr in
hypereutrophic drinking water lakes. J. Phycol. 1995, 31, 248−263.
(98) Algae and cyanobacteria in fresh water. In Guidelines for Safe
Recreational Water Environments, Coastal and Fresh Waters; World
Health Organization (WHO): Geneva, Switzerland, 2003.
(99) Barinova, S. S.; Petrovand, A.; Nevo1, E. Comparative analysis
of algal biodiversity in the rivers of Israel. Cent. Eur. J. Biol. 2011, 6,
246−259.
(100) Markina, Z. V.; Aizdaicher, N. A. Phaeodactylum tricornutum
Bohlin bioassay of water quality of Amur Bay (the Sea of Japan).
Contemp. Probl. Ecol. 2011, 4, 74−79.
(101) U.S. Environmental Protection Agency (EPA). National
Pollutant Discharge Elimination System (NPDES), Clean Water Act
(section 303(b)(1)(c)) and NPDES regulations (40 CFR 122.44(d)),
1977.
7084

(102) Verity, P. G. Expansion of potentially harmful algal taxa in a
Georgia Estuary (USA). Harmful Algae 2010, 9, 144−152.
(103) Zurawell, R. W.; Chen, H.; Burke, J. M.; Prepas, E. E.
Hepatotoxic cyanobacteria: A review of the biological importance of
microcystins in freshwater environments. J. Toxicol. Environ. Health
2005, 8, 1−37.
(104) Van Dolah, F. M. Marine algal toxins: Origins, health effects,
and their increased occurrence. Environ. Health Perspect. 2000, 108,
133−141.
(105) Landsberg, J. H.; Balazs, G. H.; Steidinger, K. A.; Baden, D. G.;
Work, T. M.; Russel, D. J. The potential role of natural tumor
promoters in marine turtle fibropapillomatosis. J. Aquat. Anim. Health
1999, 11, 199−210.
(106) Edmunds, J. S.; McCarthy, R. A.; Ramsdell, J. S. Ciguatoxin
reduces larval survivability in finfish. Toxicon 1999, 37, 1827−1832.
(107) Landsberg, J. H.; Balazs, G. H.; Steidinger, K. A.; Baden, D. G.;
Work, T. M.; Russel, D. J. The potential role of natural tumor
promoters in marine turtle fibropapillomatosis. J. Aquat. Anim. Health
1999, 11, 199−210.
(108) Landsberg, J. H., Steidinger, K. A. A historical review of
Gymnodinium breve red tides implicated in mass mortalities of the
manatee (Trichechus manatus latirostris) in Florida, USA. In Proceedings
of the 8th International Conference on Harmful Algae; Reguera, B.,
Blanco, J., Fernandez, M., Wyatt, T., Eds.; Xunta de Galicia-IOC/
Unesco: Vigo, Spain, 1998; pp 97−100.
(109) Anderson, D. M., Toxic algal blooms and red tides: A Global
Perspective. In Red Tides: Biology, Environmental Science and
Toxicology; Okaichi, T., Anderson, D. M., Nemoto, T., Eds.; Elsevier:
New York, 1989; pp 11−16.
(110) Smayda, T. J., Novel and nuisance phytoplankton blooms in
the sea: Evidence for a global epidemic. In Toxic Marine Phytoplankton;
Graneli, E., Sundstrom, B., Edler, L., Anderson, D. M., Eds.; Elsevier:
New York, 1990; pp 29−40.
(111) Rhodes, L. L.; Mackenzie, A. L.; Kaspar, H. F.; Todd, K. E.
Harmful algae and mariculture in New Zealand. J. Mar. Sci 2001, 58,
398−403.
(112) Weissman, J. C., Benemann, J. R., Comparison of Marine
Microalgae Culture Systems, Second National Conference on Carbon
Sequestration, 2003. http://www.netl.doe.gov/publications/
proceedings/03/carbon-seq/PDFs/217.pdf (accessed December 20,
2011).
(113) Benemann, J., Pedroni, P. M., Davison, J., Beckert, H.,
Bergman, P., Technology roadmap for biofixation of CO2 and
greenhouse gas abatement with microalgae. In Second National
Conference on Carbon Sequestration, 2003. http://www.netl.doe.gov/
publications/proceedings/03/carbon-seq/PDFs/017.pdf (accessed
December 20, 2011).
(114) Chisti, Y. Microalgae as sustainable cell factories. Environ. Eng.
Manage. J 2006, 5, 261−274.
(115) Bhatnagar, A., Bhatnagar, M.. In Innovative Approaches in
Microbiology; Maheshwari, D. K., Dubey, R. C., Eds.; India, Bishen
Singh Mahendra Pal Singh: Dehra Dun, 2001; pp 379−403.
(116) Bhatnagar, A.; Bhatnagar, M.; Chinnasamy, S.; Das, K. C.
Chlorella minutissimaA promising fuel alga for cultivation in
municipal wastewaters. Appl. Biochem. Biotechnol. 2010, 161, 523−536.
(117) Woertz, I.; Feffer, A.; Lundquist, T.; Nelson, Y. Algae grown
on dairy and municipal wastewater for simultaneous nutrient removal
and lipid production for biofuel feedstock. J. Environ. Eng. 2009, 135,
1115−1122.
(118) Chinnasamy, S.; Ramakrishnan, B.; Bhatnagar, A.; Das, K. C.
Biomass production potential of a wastewater alga Chlorella vulgaris
ARC 1 under elevated levels of CO2 and temperature. Int. J. Mol. Sci.
2009, 10, 518−532.
(119) Francisco, E. C.; Neves, D. B.; Jacob-Lopes, E.; Franco, T. T.
Microalgae as feedstock for biodiesel production: Carbon dioxide
sequestration, lipid production and biofuel quality. J. Chem. Technol.
Biotechnol. 2010, 85, 395−403.
(120) Hemmingsen, J. G.; Møller, P.; Klenø Nøjgaard, J.; Roursgaard,
M.; Loft, S. Oxidative stress, genotoxicity, and vascular cell adhesion
molecule expression in cells exposed to particulate matter from
combustion of conventional diesel and methyl ester biodiesel blends.
Environ. Sci. Technol. 2011, 45 (19), 8545−8551.
(121) Energy.Gov, Department of energy announces $24 million for
algal biofuels research, 2010. http://energy.gov/articles/department-
energy-announces-24-million-algal-biofuels-research (accessed Decem-
ber 21, 2011).
(122) National Renewable Energy Laboratory (NREL), Algal
Biofuels R&D at NREL, 2010. http://www.nrel.gov/docs/fy10osti/
49123.pdf (accessed December 21, 2011).
(123) U.S. Department of Agriculture (USDA) Rural Development,
Section 9005, Bioenergy Program for Advanced Biofuels Payments to
Advanced Biofuel Producers. http://www.rurdev.usda.gov/BCP_
Biofuels.html (accessed December 21, 2011).
(124) Energy. Gov., Secretaries Chu and Vilsack announce more than
$600 million investment in advanced biorefinery projects, 2009.
http://energy.gov/articles/secretaries-chu-and-vilsack-announce-
more-600-million-investment-advanced-biorefinery (accessed Decem-
ber 21, 2011).
(125) Algae Industry Magazine.Com, Money, U.S. DOE Awards
$100 million to three algae biorefineries, 2011. http://www.
algaeindustrymagazine.com/u-s-d-o-e/ (accessed December 21, 2011).
(126) Federal Register, Vol. 76, No. 48, Friday, March 11, 2011,
Notices, 13345, Department of Agriculture, Rural Business-Cooper-
ative Service, Rural Utilities Service, Notice of Contract Proposal
(NOCP) for Payments to Eligible Advanced Biofuel Producers.
http://edocket.access.gpo.gov/2011/pdf/2011-5573.pdf (accessed
December 21, 2011).
(127) Hileman, B., Views differ sharply over benefits, risks of
agricultural biotechnology, Chem. Eng. News, 1995.
(128) Menetrez, M. Y. The potential environmental impact of waste
from cellulosic ethanol production. J. Air Waste Manage. Assoc. 2010,
60, 245−250, DOI: 10.3155/1047-3289.60.2.245.
(129) Energy Independence and Security Act of 2007 (EISA 2007),
Pub. L. 110−140.
(130) Foley, P. M.; Beach, E. S.; Zimmerman, J. B. Algae as a source
of renewable chemicals: Opportunities and challenges. Green Chem.
2011, 13, 1399−1405.
7085

An Overview Of Algae Biofuel Production And Potential Environmental Impact

Recommended

Recommended

More Related Content

Similar to An Overview Of Algae Biofuel Production And Potential Environmental Impact

Similar to An Overview Of Algae Biofuel Production And Potential Environmental Impact (20)

More from Anita Miller

More from Anita Miller (20)

Recently uploaded

Recently uploaded (20)

An Overview Of Algae Biofuel Production And Potential Environmental Impact